1. Field of Invention
The invention relates generally to a method and system for automatically provisioning an overhead byte used in transmitting information in a communications network.
2. Description of Related Art
Within the evolving telecommunications industry, the advent of numerous independent, localized networks has created a need for reliable inter-network communication. Unfortunately, this inter-network communication is difficult to accomplish in a cost effective manner due to differences in the digital signal hierarchies, the encoding techniques and the multiplexing strategies. Transporting a signal to a different network often requires a multiplexing/demultiplexing, coding/decoding process to convert the signal from one scheme to another scheme. To address these difficulties, standards for network communications have been developed. One standard referred to as SONET, an acronym for Synchronous Optical NETwork, defines a set of standards for the rates and formats for optical networks. Proposed by Bellcore during the early 80s and standardized by ANSI, SONET is compatible with Synchronous Digital Hierarchy (SDH), a similar standard established in Europe by ITU-T.
FIG. 1 depicts a Synchronous Transport Signal (STS) frame that forms the basic building block of SONET optical interfaces, where an STS-1 (level 1) frame is the basic signal rate of SONET. Multiple STS-1 frames may be concatenated to form STS-N frames, where the individual STS-1 signals are byte interleaved. The STS-1 frame consists of 90 columns by 9 rows of bytes, the frame length is 125 microseconds. As such, the STS-1 frame has a rate of 51.840 Mb/s. The STS-1 frame shown in FIG. 1 depicts the byte allocation in the section overhead (SOH), line overhead (LOH) and path overhead (POH). The synchronous payload envelope (SPE) carries the information portion of the signal along with the POH. The various overhead bytes carry signaling and protocol information. This allows communication between intelligent nodes within the network, permitting administration, surveillance, provisioning and control of the network from a central location. The SDH standard is similar to the SONET standard and includes similar overhead bytes arranged in a synchronous transport module (STM).
Existing communications networks are continually under pressure to increase capacity by carrying increasingly higher data rates and also non-SONET, packet based signals. Due to the proliferation of non-SONET signals, it is important that bandwidth on an optical transmission system be utilized efficiently. Therefore, there is a need to multiplex non-SONET signals. One way to perform this multiplexing is to map the non-SONET format signals into SONET frames to exploit the advantages afforded by SONET. Since the non-SONET format signals (e.g., GbE) have a lower data rate than SONET frames, two or more signals can be multiplexed onto a single wavelength. In these cases it is advantageous to be able to direct the two multiplexed streams to different destinations. Accordingly, there is a need in the art for a system that automatically provides for directing multiplexed signals to different recipients in a communications network.